Combustion-chamber-pressure regulator



' Dec. 21 1926.

' c. H. SMOOT COMBUSTION CHAMBER PRESSURE REGULATOR INVENTOR CH/mz 553/7. 604007 Filed July 51,

vl atented Dec.'2l, 1926.

COMBUSTION-OHAMBER-PRESSURE REGULATOR.

Application filed July 31, 1925. Serial No. 47,293.

The present invention has for its object the regulationof the pressure .of the gases, in a furnace 1n suchmanner and by such mears as will insure the maintenance at all times of the proper degree of negative pressure with respect to, the atmosphere independently-of fluctuations of other functions such as thickness of fuel bed; pressure of forced draft or the like. It is desirable that the pressure increase its negative value with increase in furnace rating, i. e. with increase in air volume. The combinations described "and claimed herein accomplish these objectsby a control of the stack or outlet damper which control is responsive to the pressure of'the gases in the furnace;v devices responsive to the pressure of the furnace gases, properlypro- 'portioned, or properly loaded, are so con nected to the stack or outlet damper as to give the same a definite pressure adjustment for each rating of the furnace to the end i that as the air-volume increases, the presis quadrupled.

sure in the furnace will be increased in negative value in quadrature, that is to say, if for example the rating and hence the air volume is doubled the negative pressure A. chief advantage flowing from this condition is that the leakage through .the furnace walls will always be inward and its amount proportional at all times to the furnace rating, the leakage being greater as the furnace becomes hotter, which is conducive both to economy and durability. The heat released will be carried off quicker as the rating increases and in that way the brick work will be protected against any soaking effect. A principal feature of the invention is a duplex damper control, one element of which is made responsive to the pressure just above the fire and the other element responsive to the pressure just ahead of the stack damper, the latter element being designed to act jointly with the former element for the purpose of giving a movement to the damper and effect the increasein negative pressure above referred to. As the pressure in the stack is more negative than in: the fire box, its control element is made s maller or has' its force reduced so that it will not have an exaggerated influence on the control, and means are provided for accurately adjusting its efiect. a t

An application of the invention is shown in the accoi-npanying drawings in which- Figure 1 is a diagrammatic sectional view of a boiler furnace.

Figure 2 is a diagram showing the ordinary relation bet-ween the combustion cham ber pressure and the stack pressure, and Figure is a similar diagram showing how this relation is changed by the appli-- cation of my regulator.

A boiler 1 has a combustion chamber 2,

astack 3 provided with a stack damper,

and an air supply pipe 5 in which is shown a damper Gas a means of controlling the volume of air admitted to the furnace.-

The stack damper 1 is connected by crank arm 7 and 8 and lover 9 to a rod 10 attached to a diaphragm 11 operating in a casing 12. The lever 9 is pivoted to a fixed support at 13 and may have an adjustable loading means as for example a spring 14:, the tension of which may be changed by screw 15. The rod 10 may have a piston 16 operating in a cylinder 17 to 'act as a retarding device. The chamber 17 above the dia phragm is connected by pipe 18 to the combustio'ri chamber 2 while the chamber 19 below the diaphragm is connected bypipe 20 to the stack just below the stack damper.

A pipe 21 leads ofi from pipe 20 to the atmosphere and furnishes a means of reducing the suction in pipe 20 and therefore also in chamber 19. Cooke 22 and 23 in the air inlet pipe 21 and the stack pressure pipe-20 respectively furnish means for frac:

tioning the suction in the stack to the desired amount so that the pressure in chamber 19 will balance the combustion chamber pressure existing in chamber 17. Thus if draft will be slight, and the pressure in the combustion chamber will be but slightly less than atmosphere. An increase in air supply to the fire following an increased demand on the furnace will initially raisethe pressure in the combustion chamber a slight p the increase in suction below the damper will;

i diaphragm and thus the desired increase in; I negative pressure can be obtained, the ideal conditions being formed when thesuction amount, thus reducing the suction on top of the diaphragm. The diaphragm will then move to open, the damper.

in the suction below the damper andalso an increase in suction but of less amount just above the fuel bed. A small proportion of be communicated to the undersideof the diaphragm and this will cause the damper to open still further and thusgive a suction in the combustion. chamber greater than if the latter pressure alone was the controlling element. By adjusting the cooks 22 and 23,

any fraction of the stack suction can be allowed to pass to the underside of the increases as the square of the furnace rating. It will be understood that with the new setv ting. of the damper thus brought about by- '-a change in furnace rating, the diaphragm will again be in equilibrium but with slightly greater suction on its top side,-and consequently in the furnace over the fire, and also a correspondingly greater suction on its underside corresponding to a fraction of the much greater suction in the stack below the dampen It will be seen that the furnace pressure control is held at the proper negative value irrespective of all other variables .having to do with the operation of the furnace. The fuel bed .may be thick or thin; the

pressure, of the forced draft may be great or small; the controller will'insure the mega tive pressure quite independently of them and independently of their means of control, but will always give an increasing negative furnace pressure corresponding to an increasing rating and air volume supply. The

mathematical relations may be illustrated-by the diagrams Figures 2 and 3. a

- hese figures the vertical dimensions indicate the suction or negative pressure,

with respect to, the atmosphere while the horizontal dimensions indicate the load or boiler rating. In ordinary practice the com- -bustionqchamber pressure is maintained at a fixed negative value, as shown by the horizontal line on p of Fig. 2. The nega-- t1ve stack pressure as shown by the curve increases with the square of the rating.

Figure 3 shows the result on the combustion.

chamber pressure when the regulator descrlbed above is in operation. Here the negative'combfistion chamber pressure 0 c 79 is also increased as the square of the rating; the curves at, b, 0, representing the fluctuations of the stack? pressure having corresponding curves a, b, a, for the combustion o amber pressure. P being the combustion chamber pressure, P the stack pressure, and K a constant, their the boiler differential Such opening of the damper willbe followed by an increase tion the qualification element by (P -P is connected to boiler by formula The regulator introduces into this equathe rating R of the stack damper until where n is the ratio desired to be maintained between the twopressures By substituting the equivalent of P in the formula we have:

" nP-P =R%K=P (n i) or i . i K 2 2 I P R on so that P, becomes a definite function of it.- In other wordsthe combustionchamber pres 'surevaries in exact proportion with the reducing the'stack pressure to bring it down in force to a .point where it can be made to balance the combustion chamber pressure. I claimse moving the -1. A furnace'pressure control comprising a an outlet damper, means responsive to combustion chamber pressure, and to a fraction of the pressure just preceding the damper to control the setting of. the said damper to the combustion chamber in greater ratio than the variation in the furnace rating.

effect a variation in the negative pressure in 2. A furnacepre ssure control comprising i an outletdamper, means responsive to, combustion chamberpressure and to a fraction of the pressure just preceding the damper to control-the setting of the said damper to effect a Variation in the negative pressure in the" furnace proportional to the square of the furnace rating.

3.-A furnace pressure control com rising moving memberresponsive to the pressure in said chamber connected to the damper, a

astack damper, a chamber connected y pipe .With the combustion chamber and having a chamber connected by pipes with the stack I to the pressure'in which said moving membjer is also'responsive so thatthe pressures in the chambers act oppositely on the member, and means for reducing the force of the stack pressure to establish a definite ratio between the combustion chamber pressure and ;the I pressure in the stack.

4.. A furnace pressure control comprisin a'stack damper, a chamber connec ted by pipe with thecombustion chamberand having a moving member responsive to the pressure in said chamber connected to the damper, a chamber connected "by pipes with the stack ltothe pressure in'which said-moving member 1s also responslve so that the pressures moving member responsive to thepressure in said chamber connected to the damper, a

chamber connected by pipes with the stack to the pressure in which said moving memher is also responsive so that the-pressures in the chambers act-opposltely on themember means for fractioning the stack pressure atmosphere. I

before it reaches its connected chamber said means comprising an adjustable outlet to the atmosphere from the pipes connecting the stack with the chamber,-and an adjusting valve in the connecting pipe for restrict ing the flow to the stack from the atmosphere.

' 6. A furnace pressure control comprising a damper for the regulation of furnace pres- ,sure which is responsive to furnace pressure on the one hand'and a-second pressure inter-. mediate between that of external atmosphere and stack an adjusta 1e negative pressure is maintained in the combustion chamber.

7 .A' furnace pressure control comprising means for varying the furnace pressure actuated by means responsive to the furnace pressure and to some other pressure interthe stack pressure and mediate between cHA'RnEs H. SMOOT.

ressure of. the furnace whereby 

